Topological flow characteristics in a butterfly valve used for a spark ignition engine

The flow fields in a butterfly valve, consisting of a circular cylinder and a circular plate with a circular shaft, are numerically investigated with changing the valve angle, i.e., 15°, 45°, 75° and 90° (full-open). The corresponding Reynolds numbers are chosen as 10⁴, 4 × 10⁴, 7 × 10⁴, and 10⁵. The pressure drops between the entrance and the exit of the valve are 0.904, 0.575, 0.382 and 0.199, respectively at the above four valve positions. The moment coefficients calculated for the valve shaft are mostly due to the unbalanced pressure distribution on the both sides of the valve plate and -0.365, -0.082, -0.033 and 0, respectively, for each valve angle. The pressure distribution on the valve cylinder and the topological streamline patterns qualitatively show the flow field exceedingly agitated by the valve plate and its shaft.